The invention relates to a reactor for treating liquids with a view to remove impurities by electrochemical means.
Liquids such as waste water have traditionally been cleaned by means of chemical and biological treatment and sedimentation. Oxidation is performed in aerators, and micro-organisms will deal with nutrient salts as well as with heavy metal ions. These processes are not difficult to perform but they require large plants and considerable process time. Hence they are frequently performed on waste water and not on fresh water pumped up for consumption or on surface water. For waste water it has become standard practice to perform membrane filtration, for example in the form of reverse osmosis for salt removal and micro filtration for removal of micro-organisms. Sometimes chlorination, UV-radiation and ozonification is used. Such plants are, however, very complex, and their working pressures have to be large which puts heavy requirements on the pumps involved. Hitherto known purifying plants are normally constructed according to the removal of specific impurities, and modifications to perform optimally for other impurities, which may appear, are complex and time consuming.
Production enterprises have today to pay for the degree of pollution of their effluents which often represents a significant expense in production operation and involve the costs of the installation of large purification facilities within the production plant in question.
There is hence a hitherto unfilled need for an apparatus or reactor which is easily adaptable to changing purifying requirements and which does not require large plants of very high operating pressures.
It is known that electrochemical processes may have a biocidal effect on the bacteria content in a treated liquid due to the electrical current. It is also well known to produce a mechanical, catalytic and magnetic stimulation of the oxidation/reduction processes of organic substances in waste water. By using a reactor with a heterogeneous electro-chemical action it is feasible to solve the problems outlined above. However, existing equipment which is available for electrochemical processes is designed for the synthesis of organic or metallo-organic compounds and is not well suited for treating large volume flows of liquid, such as waste water. Mere re-configuration of equipment of the known type to achieve this aim has not hitherto proved economical.
It is therefore a purpose invention to provide an apparatus or reactor which is well suited to the purifying processes envisaged and which is adaptable to a wide range of flows and effluent parameters and in which it is simple to provide further specific functionalities for existing purifying plants.
This is obtained by means of a reactor according to the invention in a process in which the liquid, such an aqueous solution, is passed between a series of plateshaped, corrugated reaction electrodes with a volume speed which is above a minimum to prevent dissociation into constituent gases but sufficient to ensure interaction with an electrical current passing between the reaction electrodes, which are electrically insulated against each other, the reactor being particular in that it comprises at least one and preferably more interconnected units with series of plateshaped electrodes, valve means and holes in the plates for redirecting the liquid flow into and through the series of reaction electrodes, and an automatic electronic control system consisting of a number of sensors at the liquid inlet of the reactor for measuring the conductivity of the treated liquid, the organic contents of the liquid and the flow (volume) of the liquid, means for transferring the measurements to a processor for further treatment, and means for transferring the output commands from the processor to the valve means for redirecting the liquid flow and for activating or deactivating the electrode unit or units in dependence on the measured parameters.
To enable simple, fast and efficient changes in the passing flow while using standardized electrode plates, a preferred embodiment of the invention is particular in that the electrical insulation between the plates is shaped as liquid tightening gasket sealings acting as manifolds and flow controllers. A further embodiment is particular in that the processor also includes means for adjusting the density of the electrical current passing between the plates.
Another advantageous embodiment in particular is that at least some electrode surfaces are coated with layers of catalytic compounds including pure metals.
In a further advantageous embodiment the electro-chemical process plates are interspersed with heat exchanger plates to obtain a better temperature control of the process and to recover the heat from the treated liquid.
Yet another advantageous embodiment comprises the placement of separation membranes between one or more electrode pairs.
In a further advantageous embodiment specially shaped electromagnets are connected with some of the plateshaped electrodes to provide a magnetic field in the space between an electrode pair and thus stimulate the process between the plates.
In a further advantageous embodiment ultrasonic actuating devices are fitted into the manifolds of the single units to likewise stimulate the process between the plates of the unit in question thereby increasing the efficiency of the process. Gases are formed by the electro-chemical reaction between electrodes and if the gases are allowed to accumulate they get larger and larger with the result, that the gases generated to work in the process gets lost to the solution. By using ultrasound the gas bubbles are stimulated to expand and then implode, whereby the gases are returned to the solution. An additional advantage in this connection is a cleaning effect upon the electrodes during the process.
All the above embodiments allow for the inclusion of the reactor into existing heat exchanger installations of purifying systems for waste water in order to pre-process the effluent before it is lead into sewage systems, and due to its modest outer dimensions and simple construction principals the reactor provides thus a surprising new means for purifying of effluents.